Transmission type illuminating device for stereomicroscopes

ABSTRACT

A transmission type illuminating device for stereomicroscopes formed by arranging in the order mentioned a light source, a collector lens, a pair of light source image forming lenses located in positions symmetrical with respect to the optical axis of the collector lens and a relay lens for light source images arranged on the same optical axis as of the collector lens in order that a uniform bright illumination may be always made irrespective of the magnification and a wide uniform oblique light illumination may be also easily made. The light source is arranged in a position conjugate with a sample placing surface with respect to the collector lens and relay lens for the light source image and the pair of light source image forming lenses are so arranged that their respective optical axis may coincide respectively with a pair of rays from the light source intersecting at the sample placing surface and respectively entering a pair of entrance pupils of a stereomicroscope and the light source images to be formed by the pair of light source image forming lenses may be in positions conjugate respectively with the above mentioned pair of entrance pupils with respect to the relay lens for light source images.

BACKGROUND OF THE INVENTION

(a) Field of the invention

This invention relates to a transmission type illuminating device for stereomicroscopes.

(b) Description of the prior art

In such conventional transmission type illuminating device of the kind as is disclosed, for example, in Japanese Utility Model Laid-Open No. 5808/1966, a frosted glass is arranged in a position conjugate with the entrance pupil of a stereomicroscope with respect to a condensor lens and is illuminated from the back to be used as a secondary light source so that a so-called Kohler illumination may be made. However, generally, in the Kohler illumination, unless the intensity of the beam emitted from the light source is constant irrespective of the direction, a sample will not be able to be uniformly illuminated. However, there has been a problem that, in such case of a light source consisting of a frosted glass illuminated from the back as in this conventional example, the beam intensity will vary so much depending on the direction that the illumination will fluctuate. There has been also a problem that, if the surface of the frosted glass is made rougher, the illumination fluctuation will tend to reduce but, in such case, the illumination efficiency will reduce and a bright illumination will be difficult. There has been also a problem that, as there are two entrance pupils in the stereomicroscope, in order to make a Kohler illumination which is an ideal, the illuminating optical system will become complicated. Further, there has been also a problem that, though most of the stereomicroscopes have magnification varying mechanisms, the position and aperture of the entrance pupil will vary with the magnification variation. Therefore, the Kohler illumination forming the image of the light source in the entrance pupil of the observation system will become imperfect. There has been also a problem that particularly, on the high magnification side, the F number will increase so much that the observed image will become dark but, in the above mentioned conventional example, in such case, no sufficient observation light amount will be able to be secured. There has been also a problem that, in a simple objective type stereomicroscope, the magnification can be varied by varying the focal distance by replacing the objective lens or by adding an adapter lens but, in such case, the position of the entrance pupil will move so much that the position conjugate with it will deviate from the frosted glass and therefore, in the above mentioned conventional example, only when an objective lens having a specific focal distance is used, the stereomicroscope will be able to be used.

Further, in some conventional transmission type illuminating devices, in order that even a transparent sample may be observed with a high contrast, the general bright visual field illumination can be switched over to an oblique light illumination. It is so formed that the illumination light is diffused by illuminating a frosted glass from the back with a light source A and collector lens B and the diffused light is reflected with a mirror D to illuminate a sample on a stage glass E and, when an oblique light illumination is to be made,the mirror D is rotated by a proper amount with the point O as a center to incline the illuminating light entering the stage glass E. However, there has been a problem that, in the case of this conventional example, the light diffusing force of the frosted glass C can not be made strong enough to obtain a large oblique light illumination effect, the effective aperture of the collector lens B can not be made large due to the restriction in fitting and thereby particularly, in the case of an oblique light illumination, only an illumination in a limited range can be made. In the transmission type illuminating device desclosed in the above mentioned Japanese Utility Model Laid-Open No. 5808/1966, an oblique light illumination is realized by knife-edging a part of the above mentioned frosted glass to interrupt the light so as to enter only a part of the entrance pupil. However, in order to obtain a uniform illumination effect with the Kohler illumination, the intensity of the light emitted from the secondary light source must be constant irrespective of the direction and therefore, in such case that the frosted glass is a secondary light source as in the conventional example, it will be necessary to make the diffusing force of the frosted glass considerably strong. Therefore, there has been a problem that the illumination efficiency will be so low that no bright illumination will be obtained and further, in the oblique light illumination, as the light is interrupted by knife-edging a part of the frosted glass which is a secondary light source, the light amount will reduce so much that no sufficient brightness will be obtained.

SUMMARY OF THE INVENTION

In view of the above mentioned circumstances, a primary object of the present invention is to provide a transmission type illuminating device simple in the formation wherein a uniform and bright illumination can be always made irrespective of the magnification and a wide uniform oblique light illumination can be also easily made.

According to the present invention, this object is attained by comprising as arranged in the order mentioned a light source, a collector lens, a pair of light source image forming lenses located in positions symmetrical with respect to the optical axis of the collector lens and a relay lens for light source images arranged on the optical axis of the collector lens. The light source is in a position conjugate with a sample placing surface with respect to the collector lens and relay lens for light source images and the pair of light source image forming lenses are so arranged that their respective optical axes may coincide respectively with a pair of beams from the light source to intersect at the center of the sample placing surface and to respectively enter the respective centers of a pair of entrance pupils of a stereomicroscope. A pair of light source images are respectively formed by the pair of light source image forming lenses in positions conjugate respectively with the pair of entrance pupils with respect to the relay lens for light source images.

According to a preferred formation of the present invention, the pair of light source image forming lenses are replaceably provided, the light source is arranged in the front side focus position of the collector lens and the distance between the pair of light source image forming lenses and the relay lens for light source images is made adjustable so that thereby a bright invariable Kohler illumination may be possible and, even if the position of the entrance pupil is moved by the magnification varying operation of the stereomicroscope, a favorable Kohler illumination may be made.

According to another preferred formation of the present invention, any one or all of the light source, collector lens and pair of light source image forming lenses are movable in the direction vertical to the optical axis and a diffusing plate is arranged near the light source image formed by the pair of light source image forming lenses so that thereby a wide uniform oblique light illumination may be easily realized as required and further a favorable oblique illumination having no sense of difference may be made in the three-dimensional view.

According to another further preferred formation of the present invention, the pair of light source image forming lenses are provided so as to be able to move into and out of the light path and will be moved out of the light path at the time of a high magnification so that thereby an invariable uniform illumination may be made at a low magnification and a bright efficient illumination may be made at a high magnification.

This and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the optical system of a conventional transmission type illuminating device;

FIG. 2 is a view showing the optical system of an embodiment of the transmission type illuminating device according to the present invention; and

FIGS. 3 to 6 are views respectively showing the optical systems of other respectively different embodiments of the transmission type illuminating device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

To explain the present invention in detail in the following on the basis of one embodiment shown in FIG. 2, the reference numeral 1 denotes a light source, 2 denotes a collector lens, 3, 3 denote a pair of light source image forming lenses consisting of convex lens located in positions symmetrical with respect to the optical axis of the collector lens 2 and 4 denotes a relay lens for light source images and consisting of a convex lens arranged on the same optical axis as of the collector lens 2 and they are arranged in the order mentioned to form an optical system of a transmission type illuminating device. The reference numeral 5 denotes a stage glass arranged in rear of the relay lens 4 for light source images and the sample placing surface of this stage glass 5 and the light source are in positions conjugate with respect to the collector lens 2 and relay lens 4. The reference numeral 6 denotes an objective lens, 7, 7 denote a pair of first image forming lenses located in positions symmetrical with respect to the optical axis of the objective lens 6, 8, 8 denote a pair of second image forming lens located in positions symmetrical also with respect to the optical axis of the objective lens 6, 9, 9 denote aperture stops arranged respectively between the first image forming lenses 7, 7 and second image forming lenses 8, 8, 10, 10 denote a pair of image rotator prisms arranged respectively in rear of the second image forming lenses 8, 8, 11, 11 denote a pair of eyepieces arranged respectively in rear of the image rotator prisms 10, 10 and they form an optical system of a stereomicroscope so that the image of a sample placed on the stage glass 5 may be formed as erect images in positions 12, 12 by the objective lens 6, first image forming lenses 7, 7, second image forming lenses 8, 8 and image rotator prisms 10, 10 and may be magnified by the eyepieces 11, 11 so as to be observed. The reference numerals 13, 13 denote entrance pupils of this stereomicroscope. The above mentioned pair of light source image forming lenses 3, 3 are so arranged that their respective optical axes may coincide respectively with a pair of main axial rays a, a, that is, rays coming out of the light source 1, intersecting at the center of the visual field of the sample placing surface and respectively entering the respective centers of the entrance pupils 13, 13 and a pair of light source images 14 (located respectively on the main axial rays a, a) by the light source image forming lenses 3, 3 may be in positions conjugate respectively with the entrance pupils 13, 13 with respect to relay lens 4 for light source images and stage glass 5. The above mentioned pair of light source image forming lenses 3, 3 are replaceably arranged.

As the transmission type illuminating device according to the present invention is formed as described above, the illuminating beams emitted from the light source 1 will be made substantially parallel beams by the collector lens 2, a part of these beams will be made to form the light source images 14, 14 by the light source image forming lenses 3, 3 and further these light source images 14, 14 will be formed as light source images 15, 15 in the entrance pupils 13, 13 by the relay lens 4 for light source images. Therefore, the illumination by the transmission type illuminating device by the present invention will become a Kohler illumination so that a bright invariable illumination may be possible. Further, the transmission type illuminating device according to the present invention is simple in the formation as described above.

The positions and apertures of the entrance pupils 13, 13 will vary with the magnification variation of the stereomicroscope. In such case, the light source image forming lenses 3, 3 may be replaced with those as shown by the chain lines in FIG. 2 so that the light source images 14, 14 of a size fitting the entrance pupils 13, 13 may be formed respectively in positions conjugate with the varied entrance pupils 13, 13. Therefore, even if the magnification of the stereomicroscope is varied, a favorable Kohler illumination will be able to be always made. By the way, instead of replacing the light source image forming lenses 3, 3, as indicated by the dotted lines in FIG. 2, the lenses 3, 3 may be formed respectively as groups of two lenses and by adding respectively another lens the distance between the two lenses may be made variable as indicated by the arrows so that the focal distance may be varied.

FIG. 3 shows the optical system of the second embodiment. Its fundamental formation is the same as of the first embodiment. However, the position of the light source 1 is made to coincide with the front side focus position of the collector lens 2 and the distance between the pair of light source image forming lenses 3, 3 and the relay lens 4 for light source images is made adjustable as indicated by the arrows. However, the relay lens 4 is formed as a group of two lenses. Therefore, the main axial rays a, a will become parallel between the light source image forming lenses 3, 3 and relay lens 4 and therefore, even if the distance between them varies, the conjugation between the light source 1 and the sample placing surface will be maintained. Therefore, when the positions of the entrance pupils 13, 13 are moved by the magnification variation of the stereomicroscope (in such case, the main axial rays a, a will not vary), the distance between the light source image forming lenses 3, 3 and relay lens 4 will be able to be adjusted so that the positions of the light source images 14, 14 may be moved on the main axial rays a, a to form the light source images in the varied positions of the entrance pupils 13, 13 and thereby an accurate Kohler illumination may be always made.

FIG. 4 shows the optical system of the third embodiment. Therein, the light source image forming lenses 3, 3 in the above mentioned first embodiemnt are replaced with light source image forming lenses 3', 3' so that virtual images 14', 14' formed by the light source image forming lenses 3', 3' may be in positions conjugate respectively with the entrance pupils 13, 13 with respect to the relay lens 4 for light source images and the stage glass 5. Therefore, the distance between the light source image forming lenses 3', 3' and relay lens 4 will become shorter and therefore the overall length can be compacted.

FIG. 5 shows the fourth embodiment. In this embodiment, as indicated by the arrows, any one or all of the light source 1, collector lens 2 and light source image forming lenses 3, 3 are so arranged as to be movable in the direction vertical to the optical axis so that a so-called oblique light illumination illuminating a sample by applying a light in the oblique direction may be possible. The oblique light illumination is effective to observe a transparent sample by contrasting it and can be easily made as follows by the present device. That is to say, the pair of light source image forming lenses 3, 3 may be integrally moved by a proper displacement in the direction substantially vertical to their optical axis or the light source 1 may be moved by a proper displacement in the direction vertical to the optical axis of the collector lens 2 so that the pair of light source images 14, 14 may be deviated by the same displacement in the same direction with respect to the main axial rays a, a. Then, these deviated light source images 14, 14 will be relayed to the entrance pupils 13, 13 so as to form deviated light source images 15, 15 in the entrance pupils 13, 13 and to make an oblique light illumination. In this case, too, the condition of the Kohler illumination will be satisfied to make a wide uniform illumination. Further, the sample will be contrasted by the oblique light illumination in the same manner in the right and lift visual fields and therefore no sense of difference will be produced in the three-dimensional observation. By the way, instead of moving the light source 1, the collector lens 2 may be moved or all of the light source 1, collector lens 2 and pair of light source image forming lenses 3, 3; 3', 3' may be integrally moved as schematically illustrated by surrounding them with the chain lines in FIG. 4. Further, to make an oblique light illumination, as shown in FIG. 5, a frosted glass or a diffusing plate 16 treated with hydrogen fluoride on the surface may be arranged near the pair of light source images 14, 14. To explain its effect in detail, in the present transmission type illuminating device, when the position conjugate with the sample placing surface with respect to the collector lens 2 and relay lens 4 is near the collector lens 2 or near the light source 1, if the light source 1 is, for example, a halogen lamp, a ghost will be likely to be generated by the reflection or diffusion of the illuminating light by such thing located near the above mentioned conjugate position as a glass tube covering the filaments. In the case of a normal transmission type illumination, the normal illuminating light will be intense enough to give no problem as compared with such detrimental light but, in the case of making an oblique light illumination at a large angle, the deviation of the light source images 15, 15 will be so large that most of the illuminating light will escape out of the entrance pupils 13, 13 and therefore the influence of the above mentioned detrimental light will be large. However, if the diffusing plate 16 is placed near the light source images 14, 14, the light source images 14, 14 will not be fogged by the diffusing plate 16 and therefore the effect of the oblique light illumination will be retained as it is but the above mentioned detrimental light will be diffused and fogged and therefore there will be an effect of extinguishing the ghost.

FIG. 6 shows the fifth embodiment. In this embodiment, the pair of light source image forming lenses 3, 3 are provided so as to be able to integrally move into or out of predetermined positions within the light path so that the pair of light source image forming lenses 3, 3 may be inserted into the light path as illustrated by the solid lines at the time of a low magnification but may be retreated out of the light path as illustrated by the dotted lines at the time of a high magnification. Therefore, if the pair of light source image forming lenses 3, 3 are inserted into the light path as illustrated by the solid lines at the time of a low magnification, the illuminating beams emitted from the light source 1 will be made substantially parallel beams by the collector lens 2, a part of these beams will be made to form the light source images 14, 14 by the light source image forming lenses 3, 3 and further these light source images 14, 14 will be formed as light source images 15, 15 in the entrance pupils 13, 13 by the relay lens 4. Therefore, as described above, this illumination will become a Kohler illumination and therefore an invariable uniform illumination will be possible. If the light source image forming lenses 3, 3 are retreated out of the light path as illustrated by the dotted lines at the time of a high magnification, as the light source 1 is in the position conjugate with the sample placing surface of the stage glass 5 with respect to the collector lens 2 and relay lens 4 as described above, the image of the light source 1 will be formed on the sample placing surface as indicated by the dotted lines in FIG. 6 and the illumination will become critical. The critical illumination will be difficult to uniformly illuminate a wide range but will be adapted to brightly illuminate a narrow range and will have a feature that the illumination characteristics will be hardly influenced by the fluctuation of the positions of the entrance pupils 13, 13 of the stereomicroscope. Therefore, an illumination efficient at the time of a high magnification will be possible.

By the way, if a frosted glass weak in the light diffusing property or a diffusing plate 17 treated with hydrogen fluoride or the like on the surface is inserted between the collector lens 2 and the light source image forming lenses 3, 3 as shown in FIG. 6, at the time of a Kohler illumination, the light source images 14, 14 will be able to be fogged and thereby, even if the positions of the entrance pupils are somewhat varied by the magnification varying operation or the like of the stereomicroscope, an imperfect Kohler illumination will be made and will hardly fluctuate. Also, at the time of a critical illumination, the light source images formed on the sample placing surface will be able to be fogged, thereby the illumination fluctuation will be able to be reduced and the illumination range will be able to be made large. Further, at the time of a critical illumination, if a frosted glass or a diffusing plate 18 is inserted near the stage glass 5 as illustrated by the dotted lines in FIG. 6, the above mentioned effects will be able to be made larger. 

What is claimed is:
 1. A transmission type illuminating device for stereomicroscopes comprising a light source, a collector lens, a pair of light source image forming lenses located in positions symmetrical with respect to the optical axis of said collector lens and a light source image relay lens arranged on the optical axis of said collector lens, said light source, collector lens, light source image forming lenses and light source image relay lens being arranged in the order mentioned above, said light source being in a position conjugate with a sample placing surface with respect to said collector lens and relay lens, and said pair of light source image forming lenses being so arranged that their respective optical axes can be positioned such that they coincide respectively with a pair of rays from said light source to intersect at said sample placing surface, a pair of observation optical systems including means defining a pair of entrance pupils of the stereomicroscope, said light source image relay lens and said pair of observation optical systems being positioned such that a pair of light source images produced by the pair of light source image forming lenses are conjugate with respect to the entrance pupils of said observaation optical systems.
 2. A transmission type illumination device according to claim 1 wherein said pair of light source image forming lenses are replaceably provided.
 3. A transmission type illuminating device according ing to claim 1 wherein said light source is provided in the front focal point of said collector lens and the distance between said pair of light source image forming lenses and said light source image relay lens is adjustable.
 4. A transmission type illuminating device according to claim 1 wherein each of said pair of light source image forming lenses consists of a vari-focal lens system.
 5. A transmission type illuminating device according to claim 1 wherein any one of said light source, collector lens and pair of light source image forming lenses is provided movably in the direction vertical to the optical axis.
 6. A transmission type illuminating device according to claim 1 wherein said light source, collector lens and pair of light source image forming lenses are provided integrally movably in the direction vertical to the optical axis.
 7. A transmission type illuminating device according to claim 1 further comprising a light diffusing plate arranged near said pair of light source images.
 8. A transmission type illuminating device according to claim 1 wherein said pair of light source image forming lenses are so provided as to be able to move into and out of the light path.
 9. A transmission type illuminating device according to claim 8 further comprising a light diffusing plate to be inserted near said light source image relay lens when said pair of light source image forming lenses are removed.
 10. A transmission type illuminating device according to claim 1 further comprising a light diffusing plate arranged between said collector lens and pair of light source image forming lenses.
 11. A transmission type illuminating device according to claim 1 wherein each of said pair of light source image forming lenses consists of a negative lens.
 12. A transmission type illuminating device according to claim 1 wherein each of said pair of light source image forming lenses consists of a positive lens. 